The
primary motor cortex (
Brodmann area 4) is a brain region that in humans is located in the dorsal portion of the
frontal lobe. It works in association with other motor areas including
premotor cortex, the
supplementary motor area,
posterior parietal cortex, and several subcortical brain regions, to plan and execute movements. Primary motor cortex is defined anatomically as the region of cortex that contains large neurons known as
Betz cells. Betz cells, along with other cortical neurons, send long
axons down the
spinal cord to
synapse onto the interneuron circuitry of the spinal cord and also directly onto the alpha motor neurons in the spinal cord which connect to the muscles.